In a photolithography process, there is a case where openings of the resolution limit or less are arranged longitudinally and latitudinally (two-dimensionally) in a mask layer. In such a case, what is called a cross-point method is employed in which a line-and-space pattern used in exposure is formed by two separate steps and photolithography is performed for each step. Here, the line-and-space pattern used in the first exposure and the line-and-space pattern used in the second exposure are made to cross each other.
This method is most suitable to form an opening pattern of what is called a grid configuration in which the phase of the period of the positions of the openings is equal in the longitudinal and latitudinal directions. However, to form an opening pattern of a zigzag configuration in which the phases in the longitudinal and latitudinal directions are shifted, three or more line-and-space pattern formation processes are needed and the processes are complicated. Consequently, manufacturing costs are increased.